1. Field of the Invention
The present invention relates to a transfer apparatus which holds a workpiece and which automatically transfers the workpiece in accordance with the action of an actuator.
2. Description of the Related Art
Usually, a variety of transfer apparatuses are used in a factory or the like in order to automatically transport a workpiece, for example, to respective working stations. For example, a rodless cylinder is widely adopted as such a transfer apparatus, because of the following reason. That is, in the case of the rodless cylinder, the entire length with respect to the stroke length can be shortened as compared with a cylinder having a rod. Accordingly, the rodless cylinder is advantageous in that the occupying area is decreased, and the handling performance is excellent.
For example, as disclosed in Japanese Patent No. 2613337, such a rodless cylinder is provided with a cylinder and a slide table. The cylinder includes a cylinder tube and a piston which makes reciprocating movement in a bore formed in the cylinder tube. A slit, which extends in the longitudinal direction to make communication between the outside and the bore, is formed for the cylinder tube. The slit is closed by a first seal member which is engaged with the piston and a second seal member which is engaged with the slide table.
The transfer apparatus is used, in many cases, in an environment in which large amounts of coarse particulate, cutting powder, paper powder, coolant, mist and the like exist in a mixed manner. When the rodless cylinder is used as the transfer apparatus, it is feared that the dust or the like makes invasion through the gap of the slit to deteriorate the operability of the cylinder. For this reason, for example, as disclosed in Japanese Laid-Open Patent Publication No. 9-144711 (hereinafter referred to as xe2x80x9cConventional technique 1xe2x80x9d), a rodless cylinder is known, comprising a cylinder tube, a piston which is accommodated movably in the cylinder tube, a slit which extends in the longitudinal direction of the tube and which makes communication between the inside and the outside of the tube, a slider which is arranged at the outside of the cylinder tube and which is connected to the piston via the slit, and a dust-preventive cover which covers the portion of formation of the slit and which makes expansion and contraction in the longitudinal direction of the tube in accordance with the movement of the slider.
Further, as disclosed in Japanese Patent No. 2838067 (hereinafter referred to as xe2x80x9cConventional technique 2xe2x80x9d), a rodless cylinder is known, comprising a cylinder tube, a piston which is accommodated movably in the cylinder tube, a slit which extends in the longitudinal direction of the tube and which makes communication between the inside and the outside of the tube, and a slide table which is arranged at the outside of the cylinder tube and which is connected to the piston via the slit, wherein a dust-preventive cover, which covers at least a slit-forming plane of the cylinder tube, is inserted into a cover insertion hole formed for the slide table, and the slide table is allowed to make reciprocating movement along the dust-preventive cover.
However, Conventional technique 1 described above includes the dust-preventive cover which makes expansion and contraction in the longitudinal direction of the tube in accordance with the movement of the piston and the slider. Therefore, the entire size of the rodless cylinder in the longitudinal direction is lengthened in an amount corresponding to the size in a state in which the dust-preventive cover is contracted. For this reason, it is not possible to shorten the size of the rodless cylinder. In the case of Conventional technique 2 described above, the gap is generated between the dust-preventive cover and the cover insertion hole of the slide table. For this reason, a problem is pointed out such that the dust or the like tends to make invasion with ease through the gap in accordance with the movement of the slide table.
A general object of the present invention is to provide a transfer apparatus which makes it possible to effectively shorten the size in the transfer direction and achieve the excellent dust-preventive function with a simple structure.
A principal object of the present invention is to provide a transfer apparatus which makes it possible to reliably avoid any invasion of the dust or the like through the gap between a main apparatus body and a movable member via a dust-preventive member.
Another object of the present invention is to provide a transfer apparatus which makes it possible to reliably remove the dust or the like even when the dust or the like is accumulated on a dust-preventive member, by providing a scraper corresponding to a bellows-shaped configuration of the dust-preventive member.